List finders



Jrly V.23, 1957 H NEILSEN 2,799,955

LIST FINDERS Filed DSC. 16, 1954 3 Sheets-Sheet l I; 1y. 1 F15/QM. ff

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{ 1 g/ gij ww QN uw H. L. NElLSEN July 23, 1957 LIST FINDERS 3 Sheets-Sheet 2 Filed Dech- 16, 1954 July 23, v1957 H. L. NEILSEN 2,799,955

LIST F'INDERS Filed Dec. 16, 1954 3 Sheets-Sheet 5 162 153, AB w EF @H IJ KL MN op on 5T uv wx YZ 150' 132 154 INVENTOR.

United States Patent O LIST FINDERS Hldaur L. Neilsen, Metuchen, N. J.

Application December 16, 1954, Serial No. 475,685

l Claims. (Cl. 40104) This invention relates to improvements in devices which have become commonly known as list finders. Such devices consist of a number of cards or sheets, pivotally interconnected in the form of a book, and having mechanical means cooperating with cut-back or tabbed portions of the cards or sheets at a free marginal side of the book to cause the book to open at a predetermined page or card bearing, usually, a list sought to be referred to by the user of lthe device. Illustrative of the many possible uses of such a device is the fact that the pages or cards, in sequence, may contain alphabetical lists of most frequently called telephone numbers, or of yalphabetical lists of unusual or frequently misspelled words.

The present invention relates more particularly to improved multiple key means which enable the user of the list finder to open it at a pre-selected sheet .or list by merely pressing a single one of multiple keys forming a part of the device.

Such list finders, to be acceptable to the public, must not only include mechanical means permitting such selective opening but must also include means by which the device is automatically reset, for future use, each time the device is closed. These requirements have led to numerous mechanical arrangements which are complex and costly to manufacture and which are not entirely dependable in operation.

Accordingly, an important object of this invention is the provision of an improved list finder which may be selectively opened by a single operation and which, upon being closed after use thereof, automatically resets itself for future use.

Another important object is the provision of ysuch a device which is simple in structure; hence, capable of being manufactured economically and which is dependable in operation.

The foregoing, and other more or less obvious objects, are accomplished, according to this invention, by providing, for such a book of sheets or cards, a pivotal front cover which has spring means associated therewith normally urging said cover to an open position but having frictional means by which the said front cover may be releasably held in closed relation to a base, or back cover.

A list nder, according to this invention, further includes plural, separate, substantially similar and independently operable, operating levers for each alphabetical or other division of the sheets in the device; these operating levers being associated with said front cover, in juxtaposition to cut-back or tabbed portions of the sheets when the device is closed, and each Vhaving three integral operating portions; (l) a key portion, accessible to the user, for manipulation to turn the lever, (2) a cam portion which, when the lever is thus turned, pries the front cover away from the base and clear of frictional, closing engagement with the latter and permits the said front cover to pivot to its open position in response to the force of its` related spring means, and (3) a sheet lifting finger Mlee which, when the lever is thus turned, moves into lifting position underneath a cut-back or tabbed edge of one of the sheets and lifts that sheet and all sheets above it, with the cover, to open position in which the desired list is accessible for viewing or for adding entries thereon.

The mentioned levers are so shaped that their cam portions or other part or parts thereof coac't with a part of the base, when the device is manually closed, to reset the operated lever to a non-lifting position in which the sheet lifting finger thereof is clear of all the sheets, thereby conditioning the device for further use in which it may be opened to any selected sheet. It should be understood that the mentioned several parts of the levers need not necessarily be separate and distinct as the levers may be so designed that a certain part thereof may perform several of the mentioned functions.

In order to give a detailed description of this invention, two of numerous possible embodiments. thereof are shown, for illustrative purposes, in the accompanying drawings in which:

Figure l is a top plan View of a closed list nder according to a rst preferred embodiment of the invention.

Fig. 2 is a front end elevational view of the device as seen from the bottom of Fig. l.

Fig. 3 is a fragmentary, transverse, vertical sectional View, substantially on the line 3 3 of Fig. l.

Fig. 4 is a front-to-back, vertical sectional view of the device in its open condition, the section being substantially on the line 4-4 of Fig. 6.

Fig. 5 is a horizontal sectional view, substantially on the irregular line 5-5 of Fig. 4.

Fig. 6 is a transverse, vertical sectional view, substantially on the line 6-6 of Fig. 4.

Fig. 7 is a top plan View of a closed list finder, according to a second preferred embodiment of this invention.

Fig. 8 is a front end elevational view of the device illustrated in Fig. 7, portions being broken away to show certain interior parts.

Fig. 9 is a front-to-back, vertical sectional view, substantially on the line 9 9 of Fig. 8.

Fig. l0 is a perspective view of an operating lever such as is employed in said second embodiment.

Fig. l1 is a perspective view, looking at the bottom or back of an assembly of cut-back or tabbed sheets or cards suitable for use in either of the disclosed embodiments.

The first-mentioned embodiment comprises a rigid, rectangular base 20, having a flat central card supporting platform 22, and front and back footings 24, 25 provided with pads 26, preferably of soft rubber-like material. A front Wall 28 extends upwardly from front footing 24 vand together with the latter defines a trough 29 extending across the base 20. A front extension 30, conveniently sloping downwardly from the upper edge of the front wall 28, is supported therefrom, and similar rear extensions 32 are located at the two rear corners of the base. Through the latter extensions extend the opposite ends of a pivot rod 34 which pivotally supports a rigid rectangular cover 36.

The cover 36, with said base, forms an enclosure for a card assembly 38 and, to that end, has integral side walls 40, a back wall 42 and a sloping front wall 44 which intimately overlies the bases front extension Sii when the device is closed and thus limits the closing pivotal movement of the cover, as shown in broken lines in Fig. 4. The pivot rod 34 extends outwardly through suitable holesin the side walls 40 near the latters rear ends to pivotally secure the cover to the base. The opening pivotal movement of the cover is limited to the latters full line position of Fig. 4 by reason of the arrangement wherein the lower portion of the inner surface 41 of the covers back wall 42,

cover, and the ends of'thesespri'gs engagethe base and Vthe'cover totnormally u rge the latter yieldabliy Vto its open position.` However, thedevic'efmay easilyfbef closed by manuallyl pivoting the cover toits closed position-wherein it is 'frictionally held byrather tight butQnevertheless, i

releasable, frictional engagementlbetween a front rounded portion 48 'of a preferablysomewhat resilient tongue 50 whichis retained within openings 52 and V54 in thebases front wall 28 and in the bases extension`30. The rounded portion 148 extends through opening 54 into frictional engagement with a depending skirt 56 kof the covers front wall 44 to hold Vthe cover in its closed position, except when the front end of the cover has been rather forcibly pushed upwardly from the base. l with an inner shallow recess'as at 53 to receive tongue portion 48 releasably therewithin.

A round rod 60 is tixed in the side walls 40 of cover 36, and extends between said walls across the front of the cover and adjacent the top thereof, the end portions 62 of rod 60 being headed over. Pivotally mounted on rod 60 is a multiplicity of keys 64, the latter comprising elongate body portions 66, from which extend a pair of ears 68 formed with holes 70 through which rod 68 extends; Inserted between body portion 66 and rod 60, and located between the ears 68, is a small spring 72 of flat wire bent back on itself substantially at mid length and further having its leg adjacent rod 60 bent toward the latter, so as partially to encompass rod 612i,V thus maintaining spring 72 in position. Spring 72 is thus a friction means tending to maintain key 64 in any position relative to rod 60 to which it is set, and yet permitting substantially unimpeded manipulation of the key. i Y

yThe skirt 56 may be formed pressure on the top of cover 36, producing the relation of parts of Figures l and 2, a portion 76 of a selected key 64 is depressed. Supposing the AB key has been depressed, and referring to Figure 4, the body portion 66 of the key resting on the top of wall 28 forces rod 60 and with it the entire cover 36 upwardly, releasing the protruding forward portion 48 of tongue 50 from engagement in recess S8 of skirt-56 and thus permitting cover 36 to pivot up and back to the position of Figure 4 under the influence of springs 46.

Before the cover 36 starts upwardly, however, and contemporaneously with the downward movement of portion 76 of the key, the hook portion 78 of the key has engaged the tab 112 of card 82, and, as the cover moves upwardly, hook 78 lifts card 82 and all cards above it in cover 36, said hook being maintained in engagement with said tab portion 112,1arge1y by reason of the rather tight frictional association ofthe operated key 64 with Y the rod,60 as already explained. As upward pivotal motion of the cover and cards continues, less and less weight of the cards 82-106 rests on hook 78, but thetfull weight ofthe horiznotal cards is insucient to deflect hook 78 from Vits lifting position relative to card 82. The fully 'open position ofrcover V36 is best illustrated in the full line position of Figurer4. In thisposition, the included angle between base 20 and cover 36 is perhaps 91 or 92 t degrees, so thatsthe card assemblyV 38 -rests by gravity againstV cover 36 rather than against hook 78.

' Cover' V36 mayV bre'closed by pressure on the top surface thereof'.V vAs will be clear from the broken line show-- ing of Figure 4, when the cover is fully closed all the keys V64 are in the up position, that is, with their forward portions 76 raised. The change from the down posi- Front wall 44 of cover 36 is formed with a multiplicity of slots 74, and a body portion 66 of key 64 extends Y through each slot 74. The forward portion 76 of body portion 66 of each key is further twice bent so as to presentV a convex upper surface convenient for manipulation, in particular for depressing when the cover is closed for the purpose of opening it. The rear portion 78 of body portion 66 is twice bent to form a finger or hook which Y can engage cards of the Vcard assembly 38 .as more fully explained hereinafter.

The card assembly 38, which is conventional, will be described briefly in order to facilitate description of the operation Vof the device. Assembly 38V comprises, as illustrated, the fourteen cards 80, 82, 84etc., card 80being of minimum height throughout its width, and cards 82 through 106 having portions 103 equal in height to card 80, and further portions 110 of greater height equal in height among themselves and of uniformly increasing width, so as to expose thirteen tab portions 112, `which tab portions may or may not be marked with the legends, AB, CD, etc.,'to complete an assembly in which one side of each card and the adjacent side of the next card are reserved for words, names or other indicia having initials which are two consecutive letters of the alphabet. Cards 80-106 Vare further formed with open-sided slots 114;

through which extend the at, arcuate strips 116 both ends of which are attachedY to cover 36.V Thus, the exposed surfaces of cards 80, 82 in Figures 5 and 6 are reserved for indicia having the initials A and B and conveniently the VA indicia may extend on the left side of the exposed surfaces of both cards, while the B indicia may extend on the right side of the exposed surfaces of both cards. Each card is further free to move pivotally relative to cover 36 on the strips 116.Y Ofrcrourse, the particular number of cards and the distribution between them of the letters of the alphabet, or other indicia selected, are a matter of choice and governed to some extent by the particular use for which the deviceris intended.y Y

` To operate the device, which has been closed by manual 'tion of Ythe key, asoillustrated Vin full. lines at the top of Figure 4, takes place during the very last part of downA ward movement of the cover. As the cover 36 completes Vits' downward movement, the uppermost portions ofQwall 28 and extension 30 engage the under side of portion 66 ofthe keyfcausing the latter to pivot on rod 60, ,raising forward portion 76 to the ",upV position and Vdepressing, and withdrawingV the nger or hook 78 from engagement with thetab 112. The 'completion of downward movei ment' of cover 36 reengages Vthe portionv 48 of tongue 50 in the recess 58 to latch the cover shut in the closed position.

A second embodiment of the invention is illustrated` in Figures 7, 8, '9 and 10. Except insofar as specifically differentV constructions are herein described, the con-A structionand operation of the second embodiment is sub-` stantially identical to thatY of the one just described. f The'rigid rectangular base 120 Vhaspa central card sup-` porting platform 122 provided with back and front footings 124,"125,'ihaving the Vsoft rubber pads 126. *Y Rear extensions 132 of base 120 carry the pivot Vrod 134 which pivotally' supports the rectangular cover 136.v VCove'r'5136'is`a single sheet of metal having the top wall 138, integralsidewalls V140, back Ywall 142, and

front wa1l.144. Integral with front Vwall, 144 are a rev'ersely bent strip 146 "and a` platform member 148 substantially of Z#sha'pe'd cross section and having the,V

uppersubstantially horizontalplatform 150, the riser 152 and the lower substantiallyhorizontal platform 154. 'I'he platform member'148 extends across ythe front interior of cover 136.* l'

. AV coil torque spring 156 surrounds each end of rod 134 and engages cover`136 andbase 120 to urgeV cover 136 to au'substantially vertical open position. A resilientv latch-158y engages front footing 125 of base 120 when cover 136 is closed to maintain the cover releasably in closed position. 1 n Arrow of elongate parallel slots 160 extends across the. front portion of 'top 'wall 138, substantially parallel to frontQw'all 144. 'ln eachslot 160 is located a key 164, each 'key comprising' av forward portion 166 extending exteriorly'oflfcover 136, the keys'being retained within the cover by laterally extending flanges 168 which engage the under side of wall 138. Forward portions 166 have under surfaces 170. A rear portion 172 of keys 164 .constitutes a hook or finger adapted to liftingly engage the vexposed tab portions 112A of a stack of kcards 38A in a manner previously described in connection with the 'iirst embodiment.

The .top surface of keys 164 has a rearwardly facing notch 174 which engages cover 136 at the rear end 162 of slots 160. The line of boundary 162 is thus the axis of a pivotal mounting of keys 164, about which axis the keys have a limited swinging movement limited at the up position of forward portion 166 by the ange 168 and limited in the down position by the surface 170 bearing on upper platform 150, as shown in the broken line position of Figure 9.

Located between liange 168 and linger 172 on the under side of key 164 is a recess 176 in which is located the rounded upper end 178 of a toggle expansion spring 180, the latter having an elongate portion 182 extending substantially perpendicularly `from key 164 toward footing 125 of base 120 in the closed position of cover 136. Spring 180 further has a lower end portion 181 beating on member 148 at the junction of platform 154 and riser 152 when the forward portion 166 of key 164 is in up position. In such position, as shown in full lines in Fig. 9, end 178 is above the imaginary straight line, indicated Yas a broken line, between the bearing point of the springs lower end 181 and the keys axis at slot end 162; consequently, said spring urges key 164 upwardly. As seen from the broken line showing of Figure 9, when portion 166 is depressed by manipulation, the upper end portion 178 of the spring is below the imaginary line, shown as a broken line, between the lower bearing point of the spring and the axis of the key;therefore, spring 180 tends to keep portion 166 down or depressed relatively to the cover. A snap or toggle action of key 164 is thus provided in the described swinging movement between the two positions thereof.

As vmay be understood from Figure 9, the elongate portion 182-of the spring 180 bears downwardly on footing 125 somewhat more in the down than in the up position of key 164; therefore, depressing of a selected one of the keys to open the device to expose a corresponding selected card immediately causes the lower end of spring portion 182 to bear downwardly on platform 154, thereby exerting an equal and opposite force upwardly against key 164 at recess 176, which is transferred to cover 136 at slot boundary 162 and cover 136 is forced upwardly, free of latch 158, and is then carried to open position by torque springs 156.

The downward swinging movement of portion 166 of the key, while the cover is still held closed by the downward pressure of the operators finger, brings the lifting finger 172 Yof the key into lifting relation to the tab portion 112A of the related Cardin the card assembly 38A, and said card and those above it in the stack are carried upwardly with cover 136. The 'down position of portion 166 and the surface 170 thereof resting on platform 150, is shown in broken lines in Figure 9.

When cover 136 is closed by downward manual pressure on its top wall `138, the elongate portion 182 will bear on footing or platform 125 in advance of the cornplete closing, it being evident that the length of spring portion 182 exceeds the available vertical space between recess 176 and footing 125 when portion 166 is in down position. Thus, as cover 136 is forced closed, portion 182 forces key 164 Vto pivot to its up position, and the device is then ready for another cycle of operation.

In view of the evident possibility of utilizing the concept of this invention in various structural forms, this invention should be considered of the full scope as set forth in the following claims.

What is claimed is:

1. In a Ylist inder comprising a base, said base comprising a card platform, a front wall spaced forwardly from said platform and a front extension extending forwardly from said wall, said .list nder further comprising a cover pivotally mounted at the rear of said base and swingable from a substantially horizontal, closed .position to a substantially vertical, normally open position, said nder further comprising resilient means actuating said cover to open position and latch means maintaining said cover in closed position, the improvement comprising a front Vwall comprised by said cover and overlying said front extension when said cover is closed, said finder further comprising an assembly of cards pivotally mounted therein for swinging movement with said cover and resting in a stack on said platform when said cover is closed, said cards each having an exposed tab portion overhanging said platform and adjacent said front extension, said front wall of said cover being formed with a plurality of openings, and a plurality of keys pivotally connected to and inside of said cover and having forward portions extending to the exterior of said cover through said openings, said keys further having finger portions, said keys further having portions engaging said base and actuating said forward portions to an up position when said cover is closed, all said key portions being integral parts of the keys, each of said keys being located to engage the tab of a particular card, said keys further being pivotally movable by manipulation to a down position of said forward portion and said finger engaging the tab of the respective card upon such movement of said key, said key by said movement further forcing said cover upward from latched position and said resilient means thereupon carrying said cover and said particular card and the cards above it in said stack to yopen position.

2. In a list finder of the type comprising a stack of cards resting on a base and a cover pivotally attached to said base and swingable from a normally open, substantially vertical position to a substantially horizontal, closed position in which it encloses said cards and is held closed by a latch, said finder further comprising resilient means actuating said cover to open position and said cards being pivotally connected to said finder for swinging motion with said cover, each of said cards further having an exposed tab vportion facing downwardly when said cards rest Lon said base, the improvement comprising a plurality of keys pivotally connected in and to said cover and having forward portions extending exteriorly thereof, said keys further having rear portions constituting fingers, said keys being so located that a finger 'of one key may engage the tab portion of a particular card, said keys further having portions engaging said base and forcing said forward portions to an up position when said cover is closed, said forward portions further .being swingable by manipulation to a down position, in which position of said key the nger portion thereof liftingly engages the tab portion of the key's particular card, all said key portions being integral parts of the keys, the movement of said forward portion to down position further unlatching said cover by lifting the same through engagement of said key with said base, and said resilient means thereupon lifting said cover to open position and said key carrying its respective card and the cards above it in the stack to open position along with said cover.

3. In a list nder of the type comprising a stack of cards resting on a base and a cover pivotally attached to said base and swingable from a normally open, substantially vertical position to a substantially horizontal, closed position in which it encloses said cards and is held closed by a latch, said finder further comprising resilient means actuating said cover to open position and said cards being pivotally connected to said finder for swinging motion with said cover, each of said cards further having an exposed tab portion facing downwardly when said cards rest on said base, the improvement comprising a plurality of k-eys pivotally connected in and to said cover and having forward portions extending exteriorly thereof, said keys further having integral rear portions constituting 'Y ji f 7:'f1z *fr fingers, said keys being so located that a-nger'of one key may engage Vthe'tab portion of ay particular card,

' saidforward portions further being swingable from an upV to a down position, in which down position of said forward portion said finger liftinglyengages Vthe tab por- Ytion of its respective card, and key positioning means forcing said forward portion to an up position when saidl cover is closed and further upon depressing of said for- -ward portion forcing-said cover up from said-base against the restraining influence of said latch and freeing said ycover from said latch, and said resilient means thereupon lifting said coverY to open position and said finger carrying its respective card and the cards above it in the stack to openv position along with said cover. A

4. Ina device according to Yclaim 3, said key positioning means comprising a membermounted in said cover and engaging said Vkey Vand having an elongate portion extending substantially perpendicularly from said key toward said base, said elongate portion exceeding in length the available space ybetween said basel and the engaged portion of said key in Vthe down position of said forward portion when said cover'is closed, whereby, as said cover is completing its downward movement, said elongate portion engages said base and bears upwardly against said key to lift the forward portion thereof to up position.

5. In a device according to claim 3, said key positioning means comprising a toggle spring mounted in said cover and engaging said key and having an elongate portion extending substantially perpendicularly from said key toward said base, said elongate portion exceedingin length Vthe available space between said ,base and the engaged portion of said key in the down position of said forward portion when said cover is closed, whereby, as said cover is completing its downward movement, said elongate portion engages said base and lbears upwardly against said key to lift the forward portionthereof to up position, said toggle spring providing snap action of said key between said two positions of said forward portion. 6. In alist finder of the type comprising a stack of cards resting on a base and a cover pivotally attached to said base and swingable from a normally open, substantially vertical position to a substantially horizontal, closed position in which it encloses said cards and is held closed by a latch,V said finder further comprising resilient means actuating said cover to open position Vand said cards being pivotally connected 'to said finder for swinging motion with said cover, each of said cards further having an exposed tab portion facing downwardly whensaid cards rest on said base, the improvement comprising a plurality of keys pivotally connected in and to said cover and having forward porti-ons extending exteriorly thereof, said keys further having integral rear portions constituting lingers, said keys being so located that a finger of each key may engage the tab portion of a particular card, said forward portions further being swingable from an up lto a down position, in which down posi-l tion of said forward portion said finger liftingly engages the tab portion of its respective card, said cover further being formed with a laterally extending row of substantially parallel, elongate slots and said keys being located one in Veach slot, said keys further having laterally extending flanges engaging the under side of said cover in the up position of said forward portions to limit the upward motion of the latter, said keys further being formed with a rearward facing notchron their ytop .snrface and located intermediate said rear and forward portions, and

said notches being engaged with said cover at the rearV ends of said slots and such engagement constituting the .pivotal mounting, said keys further being formed with a recess on their under surface,A and toggle springs mounted between said keys and said cover and engaging said keys in said recesses and urging said' keysagainstrsaid latter in either of its up anddown positions of its operat-. ing portion, each key thereby being adapted to snapfroin its said up to its said down position in ,response/to manual Ymovement of the operating portion from ijtsup position,

an intermediate portion' of the toggle Y springr being adapted to engage a portion associated :with said baseV .portions hrextending substantially perpendicularly from said recessesy toward said Vbase and exceeding in length theY available space between said recesses and said base .when 'said cover is closed and a key isin the down Yposition of its forward portion, said elongate portion thereby forcing Vsaid forwardfportion to-its up position when said cover is closed, and depressing ofl said forward portion forcing said cover up'from said base against the restraining iniuence of said latch and Vfreeing said cover from said latch, and said resilient means'ithereupon lifting said cover to open position and said iir'iger,V carrying its respective card and the cards above itin the stack `to open position along with said cover. Y Y f Y Y 7. In a device according to claim 6, said cover further comprising an elongate* member of I Z cross-sectional shape extending acrossV the front interior thereof and providing an upper fand a lower substantially horizontal platform and a riser toggle spring having a front end portion engaging said lower platform vand said riser -and said forward portions of said keys ha g lower surfaces bearing on said upper platform to limit their downward motion. .Y

8. YVIn aV device according to claim 7, said elongate member of Z cross-sectional shape being integral with said cover.

9.A A list Vfinder comprising a base, a cover pivotally movable relatively to said base between an open position substantially angular to said base and a closed position intimate with and substantiallyA parallel to said base, a stack' of cards, betweenV said base ,and cover, having separate,' serially and marginally arranged tabs, means yieldably pivoting said cover to its said open position, means'yieldably holding said cover in its said closed position, and plural keys pivotally associated withsaid cover, saidY keys each having a manually engageable operating portion, and, integral with the latter, a sheet holding linger which, in an up positionY of said operatingportion relatively to the cover when the latter is .in closed position, is'clear olf-'engagement with any of` said .tabs and, in a down position of said yoperating portionVY relatively to the. cover when the latter `is in closed position, is in/position to liftingly engage such a'tabV of a related card to constrain the lattervand'all cards overlying it Vto pivot with the cover to open position, and said keys each being adapted, when pivoted fromsaid up .sto saidV down positionv of its operating portion while Vthe cover is closed, .to exert a separating'force between the base and the cover to l1. A list inderaccording to claim.9, said stack-oft cards being connected to said cover and pivotal. relatively to the latterrabout an axis parallel to the axis Yof pivotal movement of said coverV relatively to said base. 12. A list finder according to claim 9, the basehaving a portion which, upon pivotal movement of thecover to its closed position, Yisarranged to engage and Vpivot theV key to move theA latters operating portionto its said up" position.

. 13. A; list finden according to claim 9, further including means coacting with said keys to inhibit pivotal movement thereof relatively tothe cover. Y Y

14. A list nder according to claim 9, further including, with respect to each of said keys, a toggle .spring coacting with the cover and the key to yieldably hold the during movement of the cover to its closedV position to so connecting said platforms,Y said extendingV transversely ofkey and said'rod to in.

alter the direction of communication of the force of said toggle spring to said key as to cause said spring to snap the key from its said down to said up position 15. A list nder according to claim 14, edge portions of the cover being within grooves in said keys to provide said pivotal association of the keys with the cover and said toggle springs continuously urging said keys toward said yedge portions to maintain such pivotal association.

References Cited in the file of this patent UNITED STATES PATENTS 

